Envelope Interface to Insulate a Post-Frame Building

ABSTRACT

This invention is an envelope-structure interface, enabling the use of exterior insulation and pressure-equalized cladding with a post-frame structure. The present invention includes the following interface details: a continuous roof-to-wall water, vapor, and air impermeable weather barrier that is fully adhered to sheathing exterior of framing, girts, and purlins; continuous roof-to-wall insulation exterior of weather barrier that is mechanically fastened back to the post-frame structure; and removal of the requirement for an interior finish material in a conditioned post-frame building. The invention brings superior envelope performance to the structural and material efficiency, rapid rate of construction, and affordability of post-frame techniques.

REFERENCE TO RELATED APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

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THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

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INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC OR AS A TEXT FILE VIA THE OFFICE ELECTRONIC FILING SYSTEM

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STATEMENT REGARDING PRIOR DISCLOSURES BY THE INVENTOR OR A JOINT INVENTOR

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BACKGROUND OF THE INVENTION

The existing problem is that post-frame construction techniques are not fully weather protected. The application of a high-performance envelope system to a post-frame structure is unpredictable due to concerns about the feasibility, safety, and efficacy thereof.

Post-frame construction has its historic origin in the agricultural sector. As farm outbuildings, these structures were frequently made of rough wood components and were not programmatically required to enclose fully conditioned space. Therefore their construction techniques have excluded details of high-performance envelopes, effectively shortening the lifespan of the building by allowing its components to weather and deteriorate. Historically, wood posts were directly set into the ground. This method drastically shortened the lifespan of the structure, and it has been only recently replaced by other methods of foundation detailing. As such, post-frame construction is poorly received by some builders of non-agricultural buildings due to perceptions of sub-standard quality.

However, post-framing construction techniques provide several advantages over other methods of building erection (e.g. stud framing). Namely, post-frame buildings of simple geometries can be erected more rapidly and with less cost in both labor and material. Therefore market opportunity exists to expand post-framing techniques to other building typologies, and especially to pair them with costly programs demanding conditioned spaces and high-performance envelopes. Despite this, post-framing has remained largely bound within the agricultural sector with limited exposure to the residential sector due to problematic envelope practices. Innovations of more robust envelope technologies for post-frame structures, such as the present invention, have been stifled by the following factors of unpredictability:

Structural Connections: In the current state of technology, thick exterior-insulated envelope systems applied to framing rely on construction types that provide vertical studs, posts, or continuous thick sheathing to mechanically fasten insulation and siding. These vertical members are at their smallest a nominal 2×4 wood stud, allowing fastener embedment to nearly the fullest depth of the member. On the other hand, the girt and purlin spacing of post-frame structures and their structural capacity to bear fasteners that hold thick exterior insulation, siding, and roofing in place are untested, to my knowledge. The horizontal orientation and structural depth of girts create safety and feasibility concerns of whether a fastener could secure embedment, thereby raising secondary concerns of wall deflection and ultimate failure under dynamic loading conditions. Further, girts span from post-to-post and are often secured at wide intervals relative to their size and orientation, creating substantial concerns of girt deflection under the loading conditions of exterior insulation and siding. Additionally, the horizontal orientation of the girt raises concerns of efficacy when driving screws obliquely from the exterior of the insulation toward the center of the girt.

Weather barrier: The current state of post-frame technology does not fully climate-protect its buildings, thereby exposing components to degradation. Specifically, buildings fail to thermally protect the weather barrier. They also fail to continuously protect all sheathing and structural framing from thermal, water, vapor, and air infiltration and fluctuation.

Interior Finish: The current state of post-frame technology utilizes an interior finish to create conditioned spaces. Interior finishes are subject to mold growth, and water and vapor infiltration due to membrane problems mentioned above. They also add cost, labor, and time.

BRIEF SUMMARY OF THE INVENTION

This invention overcomes the problems of related art and provides an envelope-structure interface that continuously protects a post-frame structure from thermal, water, vapor, and air infiltration and fluctuation. The breadth of this interface extends from the structural girts and purlins out to the wall and roof strapping, including all layers contained within.

A series of girts and purlins are regularly configured atop the underlying post and truss framing, in order to receive long, double-threaded screws that are driven from the exterior strapping through the thick insulation at intervals required to structurally support the wall assembly. The depth of the girts and purlins allows a minimum screw embedment that is sufficient to bear the dead and live loads of the wall under varying conditions. The girts, purlins, sheathing, insulation, screws, and strapping are, in conjunction, sized and configured to meet code-established deflection criteria when dynamically loaded from the exterior. These structural innovations support both a continuous sheathing substrate for a fully adhered water, vapor, and air impermeable weather barrier and a thick layer of insulation exterior of said weather barrier. Both the weather barrier and insulation layers are fully continuous from roof to wall, around the entire perimeter of the building. Finally, due to these innovations in climate control and structural systems, the present invention obviates the need for interior finishes at conditioned spaces.

Therefore, it is the purpose of the present invention to enable the construction of a post-frame building with superior envelope characteristics, thereby extending post-frame structure longevity and use in climate-controlled building typologies. The fully adhered continuous weather barrier of the present invention protects all sheathing and structural framing elements from water, vapor, and air infiltration and fluctuation, thereby preserving the structural integrity and longevity of the building. Habitability of the interior is preserved by the restriction of air flows that may carry toxins and allergens from the exterior or from the envelope assembly into the conditioned space. This characteristic of air-tightness also enables high energy performance across the envelope. Further, the layer of thick insulation continuously protects the weather barrier, sheathing, and structural framing from thermal fluctuations. This minimizes the expansion-contraction movement of the weather barrier, sheathing, and structure, and also protects these elements from damaging freeze-thaw cycles. It further ensures that the dew point rests exterior of the weather barrier; condensation therefore dries to the exterior through the vapor-permeable insulation and significantly reduces the potential for condensation-related problems at the interior. The insulation further acts as a provisional barrier to bulk water, preventing water intrusion from reaching the weather barrier itself. Moreover, the method and configuration of securing the exterior insulation minimizes both thermal bridges and aligned seams between insulation panels, thereby rendering it more effective and less prone to point failure. Finally, the removal of interior finishes at conditioned spaces reduces the required cost, time, and complexity of construction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cutaway axonometric describing the buildup of the envelope-structure interface of the present invention in context of a post-frame structure and foundation, a floor, and exterior rainscreen roofing and siding.

FIG. 2 is a cutaway axonometric from the same view angle as FIG. 1, showing the buildup of the envelope-structure interface of the present invention in isolation.

FIG. 3 is a detailed section through the bottom of the wall also highlighting the typical conditions of the wall assembly.

FIG. 4 is a detailed section through the eave condition also highlighting the typical conditions of the roof assembly.

FIG. 5 is a detailed section through the roof ridge.

FIG. 6 is a detailed section through the rake condition.

FIG. 7 is a detailed plan section through the wall corner condition.

FIG. 8 is a detailed elevation of a typical wall also highlighting insulation panel, screw, and girt configuration.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, an envelope-structure interface 22 of the present invention is shown in context of a post-frame structure 10, pressure-equalized vented roofing system 33, pressure-equalized rainscreen siding system 35, and a floor system 21. For graphic clarity, this cutaway view does not indicate the full extents of every condition.

The post-frame structure 10 is erected upon structural footings 11 and may include post bases 12. Posts 13 are anchored to the post bases 12, support roof trusses 15, and may be braced by diagonal bracing 17. Continuous lateral restraints 18 may secure the bottom chords of the roof trusses 15.

The envelope-structure interface 22 begins with girts 14 fastened on-face to the exterior of the posts 13, running the perimeter of the building. At the base of the wall, a skirt board girt 14B fastens to the base of the posts 13 to function as the bottom-most girt, also running the perimeter of the building. Purlins 16 similarly fasten to the top chords of the roof trusses 15 and run the length of the building. A continuous layer of roof sheathing 23 is fastened to the purlins 16 and abuts flush to a continuous layer of wall sheathing 24 that is fastened to the girts 14 and skirt board girt 14B. A continuous roof weather barrier 25 is applied to the roof sheathing 23 and laps over a similar continuous wall weather barrier 26 applied to the wall sheathing 24. Both weather barriers 25 and 26 are self-adhering, polyethylene-faced, polymer-modified, bituminous sheet fully adhered to the substrate in a shingle-lapped configuration from the roof ridge to the bottom of wall. Both weather barriers 25 and 26 in combination form a continuous water, vapor, and air impermeable surface at the wall and roof sheathing 23 and 24 that self-seals when penetrated. Continuous exterior roof insulation 27 is then fastened via roof strapping 29 to the underlying roof components; continuous exterior wall insulation 28 is similarly fastened via wall strapping 31 to the underlying wall components. Both roof insulation 27 and wall insulation 28 are comprised of vapor-permeable mineral wool insulation panels. Roof strapping 29 is preferably applied in-line with wall strapping 31 at regular intervals to achieve an uninterrupted ventilation pathway from the base of the wall to the eave to the ridge.

The pressure-equalized vented roofing system 33 may include roof battens 30 fastened to the roof strapping 29, or may be fastened directly to the roof strapping 29. A roof vent 34 may be secured to the ridge.

The pressure-equalized rainscreen siding system 35 is fastened to the wall strapping 31 and may also include battens (not shown). Metal flashing 32 may be applied to the outside of the exterior wall insulation 28 at grade.

A floor 21 may be bound by the skirt board girt 14B and may sit atop floor insulation 20.

The interior finish may be composed of: girts 14, purlins 16, wall sheathing 24 and roof sheathing 23.

Openings such as windows and doors are not shown for graphic clarity and are not elaborated by this description, but may be installed in a manner compliant with this envelope-interface system 22.

With reference to FIG. 2, an envelope-structure interface 22 is shown as described in FIG. 1, but shown in isolation. For graphic clarity, this cutaway view does not indicate the full extents of every condition.

With reference to FIG. 3, an envelope-structure interface 22 is shown at the base of the wall and typical wall assembly conditions are noted.

At the ground condition, a vapor barrier 21A preferably protects the skirt board girt 14B and flooring system 21 from in-ground vapor infiltration, as well as provides an opportunity to insert a thermal break between post 13 and flooring 21. The skirt board girt 14B may be set flush to the top of the flooring system 21; should the flooring system 21 be a slab-on-grade installation, the skirt board girt 14B may function as permanent formwork to bound the slab pour. The height and material of the skirt board girt 14B may vary without affecting the spirit of the present invention, though it must remain equally wide as the typical girt 14 and provide a sufficient fastening surface. The wall sheathing 24 preferably terminates at the bottom of the skirt board girt 14B while the weather barrier 26 preferably laps atop compatible vapor barrier 21A to fully seal the transitional condition. A drain mat 26A is in plane with the weather barrier 26 and wall sheathing 24, and provides a clear drainage path to weep the wall assembly. The bottom extents of the exterior wall insulation 28 and drain mat 26A depend on the flooring 21 assembly, as well as the depth of underfloor insulation 20. Wall insulation 28 may be protected from ultraviolet light and physical disturbance by metal flashing 32, which may be secured behind strapping 31.

The bottom-most typical girt 14 is located above the skirt board girt 14B at a spacing not greater than the maximum allowable for insulation 28 attachment. Typical girts 14 are wood members fastened on-face to the posts 13 and are of sufficient width and depth both to span between said posts and support live and dead loads of said wall assembly without deflecting beyond code-allowed limits, and to allow for required screw embedment. While the typical girt 14 is preferably dimensional lumber, other materials with similar structural properties may be used without affecting the spirit of the present invention. Typical girts 14 are spaced regularly at a distance not greater than the maximum allowable for insulation 28 attachment and for their structural function. Wall sheathing 24 is mechanically fastened to each girt 14 and to the skirt board girt 14B. The wall sheathing 24 is of sufficient thickness and structural properties both to span between girts 14, supporting live and dead loads of the wall assembly without deflecting beyond code-allowed limits, and to allow for required screw embedment; wall sheathing 24 is preferably plywood but may be any other board or sheet material of similar structural properties so long that it provides a continuous substrate suitable for the application of fully adhered weather barrier 26.

Thick exterior wall insulation 28, as described in the context of the present invention, is layered vapor-permeable mineral wool panels with sufficient compressive strength to resist the compression of the fastened wall strapping 31 and siding system 35 dead and live loads. This exterior wall insulation 28 is attached to the post-frame structure 10 by means of driving screws 31A and 31B from the wall strapping 31 through the insulation 28, through the self-sealing weather barrier 26, through the sheathing 24, and into the typical girt 14 or skirt board girt 14B. Screws 31A and 31B are of sufficient length to allow embedment into girt 14 and sheathing 24 to a depth sufficient to support the live and dead loads of the wall assembly, and said screws preferably have heads that allow counter-sinking into the strapping 31 so as not to interfere with rainscreen siding 35. Mechanical fastening preferably uses two lengths and orientations of screws in conjunction: longer screw 31A is driven at an oblique angle upward toward the center of each girt 14, while shorter screw 31B is driven directly toward the centerline of each girt 14. Screws 31A and 31B are preferably dual-threaded to allow simultaneous, even driving into girt 14 and wall strapping 31, while the secondary set of threads under the screw head transfer loads into strapping 31 to avoid over-compression of the insulation 28 and deformation of the wall surface. This preferable screw configuration is intended to reduce deflection under wall assembly loading.

Screws 31B may be used alone, particularly with thin wall insulation 28. Alternatively, screws 31A may be used alone.

The pressure-equalized, vented rainscreen siding system 35 may be mechanically fastened to wall strapping 31, and should include at least one open joint at the wall base of sufficient clear opening area to allow ventilation of the rainscreen cavity. Pest and insect screening (not shown) may be installed at the vent openings of the rainscreen siding 35.

With reference to FIG. 4, an envelope-structure interface 22 is shown at the eave condition where the wall meets the roof and typical roof assembly conditions are noted.

At the top of the wall, an atypical girt 14A is located above the previous typical girt 14 at a spacing not greater than the maximum allowable for insulation 28 attachment and for its structural function. This atypical girt 14A runs the length of the building and extends to the bottom of the roof sheathing 23. This condition forms a solid structural corner at the eve to provide for the fastening of roof sheathing 23, wall sheathing 24, and strapping screws 31A and 31B. Not far from atypical girt 14A is the bottom-most purlin 16, with each successive purlin 16 regularly spaced at an interval not greater than the maximum allowable for insulation 27 attachment and for their structural function. Purlins 16 are wood members fastened to the roof trusses 15 and are of sufficient width and depth both to span between said roof trusses and support live and dead loads of the roof assembly without deflecting beyond code-allowed limits, and to allow for required screw embedment. While purlins 16 are preferably dimensional lumber, other materials with similar structural properties may be used without affecting the spirit of the present invention. The roof sheathing 23 is of sufficient thickness and structural properties both to span between purlins 16 (supporting live and dead loads of the roof assembly without deflecting beyond code-allowed limits) and to allow for required screw embedment; roof sheathing 23 is preferably plywood but may be any other board or sheet material of similar structural properties so long that it provides a continuous substrate suitable for the application of fully adhered weather barrier 25. The roof sheathing 23 shingle-laps the wall sheathing 24 and is cut flush to allow continuous adhesion as the roof weather barrier 25 shingle-laps the wall weather barrier 26.

Thick exterior roof insulation 27, as described in the context of the present invention, is layered vapor-permeable mineral wool panels with sufficient compressive strength to resist the compression of the fastened roof strapping 29 and pressure-equalized vented roofing system 33 dead and live loads. This roof insulation 27 is attached to the post-frame structure 10 by means of driving a fastener 29A from the roof strapping 29 through the insulation 27, through the self-sealing weather barrier 25, through the sheathing 23, and into purlin 16. Fastener 29A is of sufficient length to allow embedment into purlin 16 and sheathing 23 to a depth sufficient to support the live and dead loads of the roof assembly, and said fastener may have a head that allows counter-sinking into the strapping 29. Mechanical fastening preferably uses a long screw 29A that is driven at an oblique angle toward the center of each purlin 16 in order to resist roof live and dead loads through tension. Screw 29A is preferably dual-threaded to allow simultaneous, even driving into purlin 16 and roof strapping 29, with the secondary set of threads under the screw head transferring loads into strapping 29 to avoid over-compression of the insulation and deformation of the roof surface. The eave condition of the roof insulation 27 is cut flush to the top of the wall insulation 28 to minimize gaps in the continuous thermal envelope, and shingle-laps the wall insulation 28 in order to assist shedding bulk water from the assemblies.

The pressure-equalized vented roofing system 33 may be mechanically fastened to roof strapping 29, or may be fastened via intermediary roof battens 30. The transition between the pressure-equalized rainscreen siding system 35 and roofing system 33 should include at least one open joint 35A at the eave, of sufficient clear opening area to allow ventilation of the assemblies. Pest and insect screening (not shown) may be installed at the vent openings of the roofing system 33.

With reference to FIG. 5, an envelope-structure interface 22 is shown at the ridge condition of the roof. While not shown, this condition could be adapted for a mono-slope roof, wherein the ridge of the roof adjoins a wall, and thus those conditions are also noted here. The pressure-equalized vented roofing system 33 should include at least intermittent ridge vents 34 to provide a ventilation outlet. The top-most purlin 16 is located close to the ridge. The roof sheathing 23 is cut flush to the roof or wall sheathing adjacent to the ridge, the roof weather barrier 25 shingle-laps the roof or wall weather barrier adjacent to the ridge, and the roof exterior insulation 27 is cut flush to the roof or wall insulation adjacent to the ridge with a positive shingle lap provided.

With reference to FIG. 6, an envelope-structure interface 22 is shown at the rake condition where the wall meets the roof. The purlins 16 run to the inside face of wall sheathing 24. The roof sheathing 23 shingle-laps the wall sheathing 24 and is cut flush to allow continuous adhesion as the roof weather barrier 25 shingle-laps the wall weather barrier 26. The roof exterior insulation 27 is cut flush to the wall exterior insulation 28 with a positive shingle lap. If girts 14 lie in-plane with the roof truss 15 at the rake condition, said girts may be either fabricated as part of the roof truss 15 or installed on site.

With reference to FIG. 7, an envelope-structure interface 22 is shown in plan at a wall corner condition. Both directions of wall girt 14 are fastened to post 13 and join each other flush at the corner. This allows wall sheathing 24 to also come to a flush corner, thereby providing a continuous substrate for a continuous wall weather barrier 26. Wall strapping 31 nearest the corner is placed proximate enough to the corner condition to support the remaining wall insulation 28 and siding 35. At the corner, wall insulation 28 is cut flush and layered (if more than one layer of insulation is required) with seams offset to minimize potential direct pathways of thermal transfer.

With reference to FIG. 8, an envelope-structure interface 22 is shown in elevation at a typical wall condition with insulation panel, screw, and girt configuration noted. Horizontal girts 14 are shown beyond for graphic clarity and are spaced at a regular interval Y up the wall.

Mineral wool insulation 28 panels may be of varying thickness and dimension. Regardless of size, a minimum of five screws 31B attach each panel, preferably in the configuration noted below. Furthermore, the screws 31B should be located proximately to the edge of an insulation 28 panel. This is preferably achieved through centering the panel seams between screw axes. This concept is shown and noted by equal dimensions W, which indicate that the vertical seams of insulation 28 panels are preferably centered between screw 31B vertical axes. Likewise, the equal dimensions V indicate that the horizontal seams of insulation 28 panels are preferably centered between screw 31B horizontal axes.

Two or more layers of insulation 28 panels are preferable, so that all seams between panels can be offset from the seams of subsequent layers of said insulation, preserving the wall assembly's thermal efficiency. Inner layer insulation panel seams 28A and outer layer insulation panel seams 28B preferably overlap as near as possible to the center of a panel, as shown.

Strapping 31 is partially shown and dashed for graphic clarity. Long screws 31B, along with the strapping 31 whose centers they penetrate, are equally spaced at a regular interval X horizontally along the wall, and at a different regular interval Y vertically up the wall, such that a preferable rectangular screw formation is achieved, where each pair of screws 31A and 31B support a tributary area complying with the loading requirements of the wall assembly. Screws 31A are not shown for graphic clarity, but their location and configuration as described in FIG. 3 corresponds with each screw 31B shown. 

What is claimed is:
 1. A wall assembly for a post-frame structure comprising the following components, in order from interior to exterior: a series of wood girts fastened to posts of said post-frame structure; a layer of sheathing fastened to said girts; a layer of water, vapor, and air impermeable weather barrier adhered to said sheathing; a layer of vapor-permeable exterior insulation; and a series of strapping members fastened by a plurality of screws that penetrate said insulation, said weather barrier, said sheathing, and embed into said girts.
 2. The wall assembly of claim 1, wherein said girts are perpendicularly oriented in relation to said posts; said girts are spaced such that both the minimum fastening requirements of said insulation are satisfied and that the maximum tributary load for said screws is not exceeded; and said girts are of sufficient size and structural properties both to span between said posts while supporting live and dead loads of said wall assembly without deflecting beyond code-allowed limits, and to allow for required embedment of said screws.
 3. The wall assembly of claim 2, wherein said girts are regularly spaced.
 4. The wall assembly of claim 3, wherein said girts are comprised of dimensional lumber.
 5. The wall assembly of claim 2, wherein said sheathing is arranged to provide a continuous substrate; and said sheathing is of sufficient thickness and structural properties both to span between said girts while supporting live and dead loads of said wall assembly without deflecting beyond code-allowed limits, and to allow for required embedment of said screws.
 6. The wall assembly of claim 5, wherein said sheathing is selected from the group comprised of plywood, wood boards, reconstituted wood panel products, and composite reinforced fiber cement boards.
 7. The wall assembly of claim 5, wherein said weather barrier is a membrane applied continuously in a shingle-lapped configuration to said substrate; and said weather barrier is self-adhering.
 8. The wall assembly of claim 7, wherein said weather barrier is self-sealing.
 9. The wall assembly of claim 8, wherein said weather barrier is comprised of a polyethylene-faced, polymer-modified, bituminous sheet.
 10. The wall assembly of claim 7, wherein said insulation is installed with continuous coverage at all wall conditions including corners and edges; and said insulation is of sufficient compressive strength to resist dead and live loads of said wall assembly.
 11. The wall assembly of claim 10, wherein said insulation is comprised of mineral wool.
 12. The wall assembly of claim 10, wherein said insulation is a single layer of insulation panels.
 13. The wall assembly of claim 10, wherein said insulation is built-up from multiple layers of insulation panels with offset panel seams.
 14. The wall assembly of claim 10, wherein said strapping is vertically oriented along the face of said insulation; said strapping is spaced such that both the minimum fastening requirements of said insulation are satisfied and that the maximum tributary load for said screws is not exceeded; and said strapping is of thickness and structural properties sufficient both to provide an adequate ventilation cavity for a vented siding system and to secure said screws without failure.
 15. The wall assembly of claim 14, wherein said strapping is selected from the group comprised of plywood, wood board, reconstituted wood panel products, wood-thermoplastic composites, and metal.
 16. The wall assembly of claim 14, wherein said screws are embedded into said girt and said sheathing to a depth sufficient to support the live and dead loads of the wall assembly; and said screws are of sufficient diameter and structural properties to withstand the loads imposed by their tributary areas.
 17. The wall assembly of claim 16, wherein said screws are double-threaded.
 18. The wall assembly of claim 16, wherein said screws are comprised of steel.
 19. The wall assembly of claim 16, wherein said screws of two configurations are used in conjunction: one perpendicular to the wall and one oblique to the wall.
 20. The wall assembly of claim 16, wherein said screws are driven perpendicularly to the wall.
 21. The wall assembly of claim 16, wherein said screws are driven obliquely to the wall.
 22. The wall assembly of claim 16, wherein a pressure-equalized rainscreen cladding system is fastened to said strapping.
 23. A roof assembly for a post-frame structure comprising the following layers, in order from interior to exterior: a series of wood purlins fastened to roof trusses of said post-frame structure; a layer of sheathing fastened to said purlins; a layer of water, vapor, and air impermeable weather barrier adhered to said sheathing; a layer of vapor-permeable exterior insulation; and a series of strapping members fastened by a plurality of screws that penetrate said insulation, said weather barrier, said sheathing, and embed into said purlins.
 24. The roof assembly of claim 23, wherein said purlins are perpendicularly oriented in relation to said trusses; said purlins are spaced such that both the minimum fastening requirements of said insulation are satisfied and that the maximum tributary load for said screws is not exceeded; and said purlins are of sufficient size and structural properties both to span between said trusses while supporting live and dead loads of said roof assembly without deflecting beyond code-allowed limits, and to allow for required embedment of said screws.
 25. The roof assembly of claim 24, wherein said purlins are regularly spaced.
 26. The roof assembly of claim 24, wherein said purlins are comprised of dimensional lumber.
 27. The roof assembly of claim 24, wherein said roof sheathing is arranged to provide a continuous substrate; said roof sheathing is cut flush with face of said wall sheathing, caps the uppermost condition of said wall sheathing without gaps, and is shingle-lapped over said wall sheathing; and said roof sheathing is of sufficient thickness and structural properties both to span between said purlins while supporting live and dead loads of said roof assembly without deflecting beyond code-allowed limits, and to allow for required embedment of said screws.
 28. The roof assembly of claim 27, wherein said sheathing is selected from the group comprised of plywood, wood boards, reconstituted wood panel products, and composite reinforced fiber cement boards.
 29. The roof assembly of claim 27, wherein said roof weather barrier is a membrane applied continuously in a shingle-lapped configuration to said substrate; said roof weather barrier shingle-laps over said wall weather barrier to form a continuous seal; and said roof weather barrier is self-adhering.
 30. The roof assembly of claim 29, wherein said weather barrier is self-sealing.
 31. The roof assembly of claim 29, wherein said weather barrier is comprised of a polyethylene-faced, polymer-modified, bituminous sheet.
 32. The roof assembly of claim 29, wherein said roof insulation is installed with continuous coverage at all roof conditions including corners and edges; said roof insulation is cut flush with face of said wall insulation, caps the uppermost condition of said wall insulation without gaps, and is shingle-lapped over said wall insulation; and said roof insulation is of sufficient compressive strength to resist dead and live loads of said roof assembly.
 33. The roof assembly of claim 32, wherein said insulation is comprised of mineral wool.
 34. The roof assembly of claim 32, wherein said insulation is a single layer of insulation panels.
 35. The roof assembly of claim 32, wherein said insulation is built-up from multiple layers of insulation panels with offset panel seams.
 36. The roof assembly of claim 32, wherein said strapping is vertically inclined following the slope of said roof; said strapping is spaced such that both the minimum fastening requirements of said insulation are satisfied and that the maximum tributary load for said screws is not exceeded; and said strapping is of thickness and structural properties sufficient both to provide an adequate ventilation cavity for a vented roofing system and to secure said screws without failure.
 37. The roof assembly of claim 36, wherein said strapping is selected from the group comprised of plywood, wood board, reconstituted wood panel products, wood-thermoplastic composites, and metal.
 38. The roof assembly of claim 36, wherein said roof strapping is aligned with said adjacent wall strapping.
 39. The roof assembly of claim 36, wherein said screws are embedded into said purlins and said sheathing to a depth sufficient to support the live and dead loads of the roof assembly; and said screws are of sufficient diameter and structural properties to withstand the loads imposed by their tributary areas.
 40. The roof assembly of claim 39, wherein said screws are double-threaded.
 41. The roof assembly of claim 39, wherein said screws are comprised of steel.
 42. The roof assembly of claim 39, wherein said screws are driven perpendicularly to said sheathing.
 43. The roof assembly of claim 39, wherein said screws are driven obliquely to said sheathing.
 44. The roof assembly of claim 39, wherein a pressure-equalized vented roofing system is fastened to said strapping. 